Their large new study found that the risk for rosacea increases among women as weight rises.

The researchers reviewed the records of nearly 90,000 U.S. women, tracked over 14 years. They found a 48 percent higher likelihood of rosacea among those with a body mass index (BMI) greater than 35 than among women of normal weight.

A BMI of 30 or higher is considered obese. For example, a 5-foot-5-inch woman weighing 180 pounds has a BMI of 30. At the same height, someone who weighs 211 pounds has a BMI of 35.

"Particularly considering the chronic, low-grade inflammatory state associated with obesity, and also the [blood vessel] changes caused by obesity, it is not surprising obesity may increase the risk of rosacea," said study author Wen-Qing Li. He's an assistant professor of dermatology and epidemiology at Brown University in Providence, R.I.

"Our study holds general public health significance, [adding] rosacea to the list of chronic diseases associated with obesity," Li said. "A healthier weight should definitely be encouraged for general health and well-being."

Rosacea is characterized by facial redness and flushing, bumps and pimples, skin thickening and eye irritation, according to the National Rosacea Society. It's estimated to affect 16 million Americans.

The condition typically develops after age 30. Symptoms can wax and wane, varying by patient. There's no cure for rosacea, which is managed with oral and topical medications, antibiotics and laser treatments, among other therapies.

Li and his team identified more than 5,200 cases of rosacea among tens of thousands of participants in the national Nurses' Health Study. They were tracked from 1991 to 2005. Not only was the risk of rosacea markedly higher among those with BMIs above 35, but there was a trend toward higher risk for rosacea among those who had gained weight after age 18.

Li said the findings may prompt dermatologists to advise their patients with rosacea to reach a normal weight to "relieve their disease," though further clinical evidence is still needed.

About a third of U.S. adults are classified as obese. Obesity has been linked to an increased risk for many health problems, including diabetes, cancer and early death, as well as inflammatory skin conditions such as psoriasis and acne.

Li also noted that his research didn't delve into the various subtypes of rosacea, which can be triggered by different factors. Also, the study only found an association between obesity and rosacea, rather than a cause-and-effect link.

"It is warranted to examine the effect of obesity on each type separately," Li said. "A large-scale clinical study would also be required to confirm that losing weight helps the relief of rosacea severity."

Dr. Ross Levy, chief of dermatology at Northern Westchester Hospital in Mount Kisco, N.Y., said he wasn't surprised by the study's findings. He agreed with Li that obesity-driven inflammation could account for the increased risk for rosacea with weight gain.

"I would never tell somebody that if you lose weight your rosacea will get better, but I would probably hint to them that it might," said Levy, who wasn't involved in the new study. "Obesity is probably the No. 1 killer in the U.S. No one thinks of it that way, but it has such a great impact on everything."

The study was published in the December issue of the Journal of the American Academy of Dermatology.